MS RFC 105: Support for WFS 2.0 (server side)

Date:

2013/11

Author:

Even Rouault

Contact:

even dot rouault at mines-paris dot org

Status:

Draft

Version:

MapServer 7.0

1. Overview

MapServer currently supports the OGC WFS 1.0.0 and 1.1.0 protocols. The latest published version of WFS 2.0, and it is desirable that MapServer implements it. Particularly in the context of the European Inspire directive that mandates WFS 2.0 as the base protocol for the INSPIRE Download Services.

2. Changes

Summary of changes in WFS 2.0

There’s apparently no official diff between WFS 1.1 and WFS 2.0, so here’s a summary :

  • GetPropertyValue

  • ListStoredQueries

  • DescribeStoredQueries

  • GetFeature with stored queries

  • new operations not covered by this work :

  • CreateStoredQuery

  • DropStoredQuery

GetCapabilities changes

There are a few changes and additions in the response document of a GetCapabilities request w.r.t WFS 1.1 :

  • the <ows:OperationsMetadata> element can have child elements that advertize which conformance classes of the specification are supported by the implementation. In the case of MapServer, we report as supported : ImplementsBasicWFS, KVPEncoding, XMLEncoding, ImplementsResultPaging. We also publish the server side limit on feature count in « CountDefault ».

  • the Filter_Capabilities respects the syntax of Filter Encoding 2.0 capabilities. It has a <fes:Conformance> element that advertizes which parts of FE 2.0 are supported by the implementation. In the case of MapServer, we report as supported : ImplementsQuery, ImplementsAdHocQuery, ImplementsResourceId, ImplementsMinStandardFilter, ImplementsStandardFilter, ImplementsMinSpatialFilter, ImplementsMinTemporalFilter and ImplementsMinimumXPath

We also now support the SECTIONS parameter of the GetCapabilities that enable the user to request only parts of the GetCapabilities document. The value of this parameter is a (comma separated) list of values among : All,ServiceIdentification, ServiceProvider,OperationsMetadata,FeatureTypeList,Filter_Capabilities

Discovered during CITE testing, we now always add the namespace prefix in the <Name> element of a feature type (could/should also probably be done for WFS 1.1.0). If no user namespace is specified, the default « ms: » prefix is used.

An example of a GetCapabilities response can be found at https://github.com/MapServer/msautotest/blob/wfs2/wxs/expected/wfs_200_caps.xml

GML 3.2.1

GML 3.2.1 defines a mandatory gml:id attribute on each geometry element : as Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon. The id will be generated as « feature_gml_id.serial_number » where feature_gml_id is the gml:id on the feature element of the geometry, and serial_number a number starting from 1 and incremented from each subgeometry (points in a multipoint, etc.)

<ms:a_layer gml:id="a_layer.1">
  <gml:boundedBy>
      <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
          <gml:lowerCorner>49.000000 2.000000</gml:lowerCorner>
          <gml:upperCorner>50.000000 3.000000</gml:upperCorner>
      </gml:Envelope>
  </gml:boundedBy>
  <ms:msGeometry>
    <gml:MultiPoint gml:id="a_layer.1.1" srsName="urn:ogc:def:crs:EPSG::4326">
      <gml:pointMembers>
        <gml:Point gml:id="a_layer.1.2">
          <gml:pos>49.000000 2.000000</gml:pos>
        </gml:Point>
        <gml:Point gml:id="a_layer.1.3">
          <gml:pos>50.000000 3.000000</gml:pos>
        </gml:Point>
      </gml:pointMembers>
    </gml:MultiPoint>
  </ms:msGeometry>
</ms:a_layer>

Regarding SRS, for WFS 2.0, it will always be reported with the « urn:ogc:def:crs:EPSG:: » syntax. This should likely also be done for WFS 1.1.0. The « wfs_return_srs_as_urn » can be set to « true » or « false » to enable or disable this behaviour. It defaults to « true » for WFS 2.0 and to « false » for older versions.

Contrary to the previous versions of WFS, WFS 2.0 in its XML Schema definition does not import any GML schema, so it is possible to generate valid GetFeature responses with other GML output formats. In particular, GML 2.1.1 and GML 3.1.1 that are already handled for WFS 1.0 and 1.1 can be used for output of DescribeFeatureType, GetFeature and GetPropertyValue.

Filter Encoding 2.0

The « PropertyName » element is replaced by a « ValueReference » element, with equivalent semantic. Likewise, the WFS 1.1 <ogc:GmlObjectId gml:id= »XXXX »/> operator is replaced by <fes:ResourceId rid= »XXXX »/>.

For the sake of compliance testing, rather dummy implementations of PropertyIsNull and PropertyIsNil operators have been introduced, as MapServer cannot generate nullable or nillable fields.

FE 2.0 MinTemporalFilter conformance class is supported with <fes:During> as operator and <gml:TimePeriod> as operand.

<fes:During>
    <fes:ValueReference>timeProperty</fes:ValueReference>
    <gml:TimePeriod gml:id="TP1">
        <gml:beginPosition>2005-05-17T00:00:00Z</gml:beginPosition>
        <gml:endPosition>2005-05-23T00:00:00Z</gml:endPosition>
    </gml:TimePeriod>
</fes:During>

Related to temporal filter, in GML 3.2.1 output, fields of type Date will be output as the following in the GML :

<ms:aFieldName gml:id="layerName.fid.aFieldName">
    <gml:timePosition>2004-01-01</gml:timePosition>
</ms:aFieldName>

And in the .xsd :

<element name="aFieldName" minOccurs="0" type="gml:TimeInstantType"/>

It is not really clear from the spec(s) if this is required, but it seems consistent with the operand of <fes:During> (a TimePeriod must match a TimeInstant).

Response paging support

Response paging was already supported in MapServer for WFS 1.1.0 as an extension. This is now a standard (optional) feature of WFS 2.0. Paging is triggered by the use of STARTINDEX (beginning at 0 for first index) and COUNT (COUNT is the equivalent of WFS 1.1 MAXFEATURES) parameters.

GetFeature operation

TYPENAME is replaced by TYPENAMES. FEATUREID is replaced by RESOURCEID.

The <gml:featureMember> element is replaced by <wfs:member>

<wfs:FeatureCollection numberReturned="X" numberMatched="Y" timeStamp="Z">
    <wfs:member>
        <ms:myElement gml_id="myElement.1">
            <ms:firstProperty>foo</ms:firstProperty>
            ...
        </ms:myElement>
    </wfs:member>
</wfs:FeatureCollection>

The FeatureCollection element has the « numberReturned » and « numberMatched » mandatory attributes.

  • numberReturned contains the number of features returned in the document (0 is always returned when RESULTTYPE=hits is specified).

  • numberMatched contains the number of features that matches the criterion of the request. If a « wfs_maxfeatures » metadata item is defined in the mapfile (or COUNT is specified in the request), « unknown » will be returned if the number of matching features reaches at least the server-side or client-side limit. This is to avoid performance issues on the server. By defining « wfs_compute_number_matched » « true », the exact number of matching features will always be computed, but this can cause performance issues.

When relevant, MapServer will fill the « next » and « previous » optional attributes that contain URL to navigate among the response pages.

The request SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=province&COUNT=1&STARTINDEX=2 will generate the following response :

<wfs:FeatureCollection
[...] numberMatched="unknown" numberReturned="1"
previous="http://localhost:8080/mapserv.cgi?SERVICE=WFS&amp;VERSION=2.0.0&amp;REQUEST=GetFeature&amp;TYPENAMES=province&amp;COUNT=1&amp;STARTINDEX=1"
next="http://localhost:8080/mapserv.cgi?SERVICE=WFS&amp;VERSION=2.0.0&amp;REQUEST=GetFeature&amp;TYPENAMES=province&amp;COUNT=1&amp;STARTINDEX=3">
[...]
</wfs:FeatureCollection>

In the case of a GetFeature request operating on several typenames, the result for each query must be in its own FeatureCollection (§ 11.3.3.5).

<wfs:FeatureCollection numberReturned="X" numberMatched="Y" timeStamp="Z">
<wfs:member>
    <wfs:FeatureCollection numberReturned="X1" numberMatched="Y1" timeStamp="Z">
    <wfs:member>
        <ms:layer1 gml_id="layer1.1">
            ...
        </ms:myElement>
        ...
    <wfs:member>
    </wfs:FeatureCollection>
</wfs:member>
<wfs:member>
    <wfs:FeatureCollection numberReturned="X2" numberMatched="Y2" timeStamp="Z">
    <wfs:member>
        <ms:layer2 gml_id="layer2.1">
            ...
        </ms:myElement>
        ...
    <wfs:member>
    </wfs:FeatureCollection>
</wfs:member>
</wfs:FeatureCollection>

Stored queries

Stored queries are queries (<wfs:Query>) stored on the server, potentially with parameters whose value can be assigned by the client during a GetFeature request.

At WEB.METADATA level, a « wfs_storedqueries » metadata item can be specified with a comma separated list of stored queries ids.

Then for each stored query id, « wfs_{storedqueryid}_inlinedef » must be specified with a valid <StoredQueryDescription> as value. As it is not always convenient to specify a inline XML content, it is also possible to specify « wfs_{storedqueryid}_filedef » whose value is a filename that contains the <StoredQueryDescription> XML content.

"wfs_storedqueries"           "bboxstoredquery"
"wfs_bboxstoredquery_filedef" "/data/bboxstoredquery.xml"

with /data/bboxstoredquery.xml containing for example :

<StoredQueryDescription xmlns:xs="http://www.w3.org/2001/XMLSchema"
                        xmlns:gml="http://www.opengis.net/gml/3.2"
                        id="bboxstoredquery">
    <Title>query title</Title>
    <Abstract>query abstract</Abstract>
    <Parameter name="longmin" type="xs:double"/>
    <Parameter name="latmin" type="xs:double"/>
    <Parameter name="longmax" type="xs:double"/>
    <Parameter name="latmax" type="xs:double"/>
    <QueryExpressionText isPrivate="false"
                        language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression"
                        xmlns:ms="http://mapserver.gis.umn.edu/mapserver"
                        returnFeatureTypes="ms:firstLayer ms:secondLayer">
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="ms:firstLayer">
            <fes:Filter>
                <fes:BBOX>
                    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
                        <gml:lowerCorner>${latmin} ${longmin}</gml:lowerCorner>
                        <gml:upperCorner>${latmax} ${longmax}</gml:upperCorner>
                    </gml:Envelope>
                </fes:BBOX>
            </fes:Filter>
        </Query>
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="ms:secondLayer">
            <fes:Filter>
                <fes:BBOX>
                    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
                        <gml:lowerCorner>${latmin} ${longmin}</gml:lowerCorner>
                        <gml:upperCorner>${latmax} ${longmax}</gml:upperCorner>
                    </gml:Envelope>
                </fes:BBOX>
            </fes:Filter>
        </Query>
    </QueryExpressionText>
</StoredQueryDescription>

A corresponding valid GetFeature request can be :

REQUEST=GetFeature&STOREDQUERY_ID=bboxstoredquery&LONGMIN=2&LATMIN=49&LONGMAX=3&LATMAX=50

Predefined urn:ogc:def:query:OGC-WFS::GetFeatureById stored query

WFS 2.0 defines a mandatory « urn:ogc:def:query:OGC-WFS::GetFeatureById » stored query. This query accept a ID parameter whose value must be a feature id.

A valid request is : REQUEST=GetFeature&STOREDQUERY_ID=urn:ogc:def:query:OGC-WFS::GetFeatureById&ID=mylayer.3

The definition hardcoded in MapServer is :

<StoredQueryDescription id="urn:ogc:def:query:OGC-WFS::GetFeatureById">
    <Title>Get feature by identifier</Title>
    <Abstract>Returns the single feature whose value is equal to the specified value of the ID argument</Abstract>
    <Parameter name="ID" xmlns:xs="http://www.w3.org/2001/XMLSchema" type="xs:string"/>
    <QueryExpressionText isPrivate="true"
                        language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression"
                        returnFeatureTypes="">
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="?">
            <fes:Filter>
                <fes:ResourceId rid="${ID}"/>
            </fes:Filter>
        </Query>
    </QueryExpressionText>
</StoredQueryDescription>

Comparing to a more standard stored query description, there are 2 oddities : The value of the « returnFeatureTypes » attribute is replaced at runtime by the name of the valid WFS layers of the mapfile (when issuing the response document to DescribeStoredQueries request). And the value of the typeNames attribute is deduced at runtime from the value of the passed ID parameter.

It is possible to override this hardcoded definition by a custom one (for example to provide alternate values for other languages) by defining « wfs_urn:ogc:def:query:OGC-WFS::GetFeatureById_inlinedef » or « wfs_urn:ogc:def:query:OGC-WFS::GetFeatureById_filedef ». The value of <QueryExpressionText> attributes and child elements must however be strictly identical to the hard-coded definition for correct execution.

A GetFeature using urn:ogc:def:query:OGC-WFS::GetFeatureById seems to be identical to a GetFeature with a RESOURCEID parameter, but there is a difference. GetFeatureById returns the feature directly as the response :

<?xml version='1.0' encoding="UTF-8" ?>
<ms:province gml:id="province.977" xmlns:ms="http://mapserver.gis.umn.edu/mapserver"
            xmlns:gml="http://www.opengis.net/gml/3.2"
            xmlns:wfs="http://www.opengis.net/wfs/2.0"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://mapserver.gis.umn.edu/mapserver http://localhost/path/to/wfs_simple?myparam=something&amp;SERVICE=WFS&amp;VERSION=2.0.0&amp;REQUEST=DescribeFeatureType&amp;TYPENAME=province&amp;OUTPUTFORMAT=application%2Fgml%2Bxml%3B%20version%3D3.2 http://www.opengis.net/wfs/2.0 http://schemas.opengis.net/wfs/2.0/wfs.xsd http://www.opengis.net/gml/3.2 http://schemas.opengis.net/gml/3.2.1/gml.xsd">
<gml:boundedBy>
    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
    <gml:lowerCorner>47.76789 -61.51051</gml:lowerCorner>
    <gml:upperCorner>47.79644 -61.45764</gml:upperCorner>
    </gml:Envelope>
</gml:boundedBy>
<ms:msGeometry>
    <gml:Polygon gml:id="province.977.1" srsName="urn:ogc:def:crs:EPSG::4326">
    <gml:exterior>
        <gml:LinearRing>
        <gml:posList srsDimension="2">47.77424 -61.51051 47.78860 -61.50894 47.79644 -61.49272 47.78743 -61.45764 47.76789 -61.45998 47.76961 -61.48350 47.77424 -61.51051 </gml:posList>
        </gml:LinearRing>
    </gml:exterior>
    </gml:Polygon>
</ms:msGeometry>
</ms:province>

ListStoredQueries

The ListStoredQueries operation has no argument and returned a simplified description of all stored queries (title and return feature types).

<?xml version="1.0" encoding="UTF-8"?>
<wfs:ListStoredQueriesResponse xmlns:wfs="http://www.opengis.net/wfs/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wfs/2.0" xsi:schemaLocation="http://www.opengis.net/wfs/2.0 http://schemas.opengis.net/wfs/2.0/wfs.xsd">
<StoredQuery id="urn:ogc:def:query:OGC-WFS::GetFeatureById">
    <Title>Get feature by identifier</Title>
    <ReturnFeatureType xmlns:ms="http://mapserver.gis.umn.edu/mapserver">ms:province</ReturnFeatureType>
    <ReturnFeatureType xmlns:ms="http://mapserver.gis.umn.edu/mapserver">ms:point</ReturnFeatureType>
    <ReturnFeatureType xmlns:ms="http://mapserver.gis.umn.edu/mapserver">ms:multipoint</ReturnFeatureType>
</StoredQuery>
<StoredQuery id="myquery">
    <Title>query title</Title>
    <ReturnFeatureType xmlns:ms="http://mapserver.gis.umn.edu/mapserver">ms:point</ReturnFeatureType>
</StoredQuery>
</wfs:ListStoredQueriesResponse>

DescribeStoredQueries

The DescribeStoredQueries operation accept an optional STOREDQUERY_ID parameter that list the ids of stored queries. If not specified, all stored queries will be returned with their full description.

MapServer will honour the value of the isPrivate attribute of <QueryExpressionText>. If defined to « true », the <Query> nodes will not be returned in the response to a DescribeStoredQueries request.

<wfs:DescribeStoredQueriesResponse xmlns:wfs="http://www.opengis.net/wfs/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wfs/2.0" xsi:schemaLocation="http://www.opengis.net/wfs/2.0 http://schemas.opengis.net/wfs/2.0/wfs.xsd">
<StoredQueryDescription id="urn:ogc:def:query:OGC-WFS::GetFeatureById">
    <Title>Get feature by identifier</Title>
    <Abstract>Returns the single feature whose value is equal to the specified value of the ID argument</Abstract>
    <Parameter xmlns:xs="http://www.w3.org/2001/XMLSchema" name="ID" type="xs:string"/>
    <QueryExpressionText xmlns:ms="http://mapserver.gis.umn.edu/mapserver" isPrivate="true" language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression" returnFeatureTypes="ms:province ms:point"/>
</StoredQueryDescription>
<StoredQueryDescription xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:fes="http://www.opengis.net/fes/2.0" id="myquery">
    <Title>query title</Title>
    <Abstract>query abstract</Abstract>
    <Parameter name="longmin" type="xs:double"/>
    <Parameter name="latmin" type="xs:double"/>
    <Parameter name="longmax" type="xs:double"/>
    <Parameter name="latmax" type="xs:double"/>
    <QueryExpressionText xmlns:ms="http://mapserver.gis.umn.edu/mapserver" isPrivate="false" language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression" returnFeatureTypes="ms:point">
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="ms:point">
            <fes:Filter>
                <fes:BBOX>
                    <fes:ValueReference>msGeometry</fes:ValueReference>
                    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
                    <gml:lowerCorner>${latmin} ${longmin}</gml:lowerCorner>
                    <gml:upperCorner>${latmax} ${longmax}</gml:upperCorner>
                    </gml:Envelope>
                </fes:BBOX>
            </fes:Filter>
        </Query>
    </QueryExpressionText>
</StoredQueryDescription>
</wfs:DescribeStoredQueriesResponse>

GetPropertyValue operation

REQUEST=GetPropertyValue&TYPENAMES=layername&VALUEREFERENCE=propertyname.

The response document has a <ValueCollection> top element and includes only the asked VALUEREFRENCE element as a child of <wfs:member>

<wfs:ValueCollection>
    <wfs:member>
        <ms:aProperty>foo</ms:aProperty>
    </wfs:member>
</wfs:ValueCollection>

Most parameters of GetFeature operation, such as FILTER, RESOURCEID, BBOX, STOREDQUERY_ID or paging, can also be used for a GetPropertyValue operation, so most of the logic of msWFSGetFeature() has been refactored so that it can be also reused by msWFSGetPropertyValue().

Sorting

Sorting was already a capability that should have been offered in WFS 1.1 but was not yet supported. We now support sorting with OGR and PostGIS connections.

Other providers relying on RDBMS (Oracle, MSSpatial, …) that support the « ORDER BY » SQL clause could be upgraded to support sorting, but this is not covered by this RFC.

MapServer shapefile provider does not support sorting. If this needed, you must use the OGR Shapefile provider.

The support for sorting relies on the following additions in mapserver.h and mapfile.c

typedef enum {
    SORT_ASC,
    SORT_DESC
} sortOrderEnum;

typedef struct {
    char* item;
    sortOrderEnum sortOrder;
} sortByProperties;

typedef struct {
    int nProperties;
    sortByProperties* properties;
} sortByClause;

struct layerObj {
  [...]
  sortByClause sortBy;
};

int msLayerSupportsSorting(layerObj *layer);
void msLayerSetSort(layerObj *layer, const sortByClause* sortBy);
char* msLayerBuildSQLOrderBy(layerObj *layer);

msLayerSupportsSorting() must be updated if a new provider supports sorting. msLayerSetSort() is called by the WFS code. And msLayerBuildSQLOrderBy() can be called by providers that implement sorting as a « ORDER BY » SQL clause, which is the case for PostGIS and OGR.

KVP and XML syntax

Both Key Value Pair (as GET, or POST) and XML syntax (as POST) are handled for all supported operations.

Optional / mandatory GML items

Tickets https://github.com/MapServer/MapServer/issues/3563 and https://github.com/MapServer/MapServer/issues/3319 raise an issue about how mandatory/optional GML items are handled. Up to now, all advertized properties in the DescribeFeatureType response documents were mandatory (since minOccurs was not specified). But when issuing a GetFeature with PROPERTYNAME, only the specified properties were returned in the GetFeature response document, which results in a document not compliant with the GML application schema.

The solution for this is to introduce a « gml_optional_items » element in the LAYER metadata. By default, now all items will be considered as optional (minOccurs= »0 » in the GML application schema). If « gml_optional_items » is specified, only the listed elements will be optional and other included items will be mandatory. This change is the most backward compatible solution for the current behaviour : only the output of DescribeFeatureType will be changed (minOccurs= »0 »), but GetFeature with PROPERTYNAME will still return only the mentioned properties. If there are more mandatory items, it might be more convenient to specify « gml_mandatory_items ».

Default behaviour with this implementation :

"gml_optional_items" "all"

All items optional except the ones mentioned :

"gml_mandatory_items" "a_required_item,another_one"

All items mandatory :

"gml_mandatory_items" "all"

All items mandatory except the ones mentioned :

"gml_optional_items"  "an_optional_item,another_one"

In addition to this, again for backward compatibility, when a GetFeature request without explicit PROPERTYNAME is processed, we will return all items, either optional or mandatory. This behaviour can now be amended by specifying « gml_default_items » to specify which items (among the optional ones) must be returned.

An example combining all the related metadata items :

"gml_include_items"   "all"
"gml_exclude_items"   "REG_CODE"
"gml_optional_items"  "all"
"gml_mandatory_items" "NAME"
"gml_default_items"   "NAME_E,NAME_F"

Inspire Download Services

INSPIRE Technical Guidance Download Services v3.1 can be implemented with Atom feeds (not supported by this RFC) and/or WFS 2.0. So we will implement Inspire D.S. conformance classes 2 (Pre-defined WFS) and 3 (Direct WFS). The mandatory conformance class « 4: Quality of Service » must be addressed by other means than the WFS 2.0 implementation itself.

Regarding mapfile configuration, the same metadata items as in « Provision of INSPIRE specific metadata » of INSPIRE View Service must be provided (in the WFS or OWS namespaces). In addition to them, for Download Services, the mandatory « wfs_inspire_dsid_code » metadata item must be set with a Spatial Data Set Identifier (or a list of identifiers separated by commas). The semantics attached to this parameter is described at paragraph 4.1.3 of the technical guidance. If needed, the namespace linked to the dataset identifier can be specified with « wfs_inspire_dsid_ns ».

Those metadata items are used to generate a <inspire_dls:ExtendedCapabilities> element in the <ows:ExtendedCapabilities> element of the GetCapabilities response document.

INSPIRE Download Services also include support for several languages. The definition of which languages are supported is done with the « wfs_languages » metadata keyword similarly to View Services. A « LANGUAGE=xxx » extra parameter in WFS KVP requests will then have effect on the GetCapabilities response documents where the information under the <ows:ServiceProvider> element as well as <Title>, <Abstract> and <ows:Keywords> in the <FeatureTypeList> section will be translated into the request language, provided that the translated version is provided in the mapfile. As an extension of the recommandations of the technical guidance, the values of the DATA and CONNECTION keywords can contain a « %language% » string that will be replaced by the requested language.

Mapfile impacts

A valid WFS 1.1 configuration can be used without modification for WFS 2.0.

INSPIRE Download Services support requires to specify the metadata items specified in an above paragraph.

3. Implementation Details

3.1 Files affected

CMakeLists.txt : add mapwfs20.c, fix a few dependency issues
mapfile.c : refactoring of msLoadProjectionString(), initialization/free of
            layer->sortBy
mapgml.c : GML 3.2.1 and WFS 2.0 GetFeature output specificities. Part of handling
           of "gml_optional_items", "gml_mandatory_items" and "gml_default_items"
mapgml.h : move some #define into another include files
mapio.h/.c : add msIO_pushStdoutToBufferAndGetOldContext() and
             msIO_restoreOldStdoutContext(), so that we can reuse without any change
             the generation of Inspire View Services extended metadata in a libxml2 DOM document
maplayer.c : new sorting functions
mapogcfilter.h/.c : Filter Encoding 2.0 support, temporal filtering, simplification
                 of existing code
mapogcfiltercommon.c : temporal filtering
mapogcsld.c: adaptation for a renaming of a function called
mapogcsos.c: adaptations for a renaming of a function called and change of prototypes
mapogr.cpp: support for a filter string that combine both a SQL where clause that
            can be passed to OGR, and a time filtering part that is processed on
            MapServer side; support for sorting
mapows.c : fixes for a few memory leaks; wfs_cite_wfs2 hack; other misc minor changes;
           add msOWSGetInspireSchemasLocation()
mapows.h : extend wfsParamsObj and gmlItemObj structures; other misc changes
mapowscommon.c : support for translation of ServiceIdentification and
                 ServiceProvider sections; support for validation of WFS 2.0
                 XML post requests
mapowscommon.h : #define for namespaces, URIs
mappostgis.c : support for sorting
mapproject.h/.c : hack for reprojection worldwide long/lat BBOX to projected SRS;
               add msIsAxisInvertedProj() and msAxisSwapShape()
mapquery.c : use only_cache_result_count flag if "wfs_compute_number_matched" "true"
             is specified; fix a bug in msQueryByRect when reprojection is involved;
mapserver.h : prototype and structure changes for sorting support; other misc changes
maptime.h/.c : const sanitization
maputil.c : add msMapSetLanguageSpecificConnection()
mapwcs11.c : adaptations for change of prototypes
mapwcs20.c : adaptations for change of prototypes
mapwfs.c : lots of changes !
mapwfs11.c : a few changes to make msWFSDumpLayer11() usable by WFS 2.0 too
mapwfs20.c : new file with the code that only applies to WFS 2.0 : GetCapabilities,
             stored queries management.
mapwms.c : adaptations for change of prototypes

3.2 Backwards Compatibility Issues

The only potential compatibility issue foreseen is related to the GetCapabilities request. Without any explicit version mentioned in the request, the WFS implementation will serve a GetCapabilities response document that conforms to the latest version of WFS it implements (as recommended by OWS 1.1), that is to say 2.0 with this new development. Which could cause confusion to WFS clients not ready to deal with it (OWS 1.1 recommand that clients specify in the ACCEPTVERSIONS parameter the list of versions they can deal with.) The solution for this is to define the wfs_getcapabilities_version keyword in the WEB.METADATA to « 1.0 » or « 1.1 ».

3.3 MapScript changes

None

3.4 Performance implications

The default configuration should exhibit the same performance as WFS 1.1.0.

Sorting might be slow on big OGR datasources that are not RDBMS drivers, such as shapefile, since a full scan of the features of the layer is done.

3.6 Restrictions

The following features are not covered by this RFC :

  • Standard, spatial or temporal joins in GetFeature operation. All are optional conformance classes of Filter Encoding 2.0

  • A very small subset of XPath 2.0 is supported (even if we shamelessly advertize ImplementsMinimumXPath to make CITE tests happy). This is limited to property names, « groupname/propertyname » syntax when using gml_group, as well as @gml:id for the VALUEREFERENCE parameter of GetPropertyValue.

  • Locking WFS

  • Transactional WFS

  • Feature versions

  • Inheritance / schema-element() XPath function

  • SOAP

  • Namespaces: the NAMESPACE KVP parameter is ignored. namespace prefixes in layer and property names are just removed.

  • the ALIAS parameter in a GetFeature request

  • the various RESOLVExxxx parameters

  • upgrade of the MapServer WFS client for WFS 2.0 protocol

3.7 Documentation

The WFS Server documentation page will be updated.

A new page will be created for Inspire Download Services with references to INSPIRE View Service.

3.8 Tests

15 new mapfiles, with more than 200 test request, have been added to test the various aspects of the implementation.

No regression has been observed on the existing WFS 1.0 or 1.1 tests.

The XML output of the expected documents has been validated against the WFS or the generated GML application schemas with the new msautotest/pymod/xmlvalidate.py script described in https://lists.osgeo.org/pipermail/mapserver-dev/2013-October/013708.html

4. Bug ID

5. OCG compliance tests

The OGC Compliance and Interoperability Testing Initiative (CITE) provides automatic tests to validate the implementation. As of today, the tests for WFS 2.0 are in beta : https://cite.opengeospatial.org/teamengine/

The implementation passes all the tests for the following conformance levels (on CITE WFS 2.0 r12 beta): - All GML application schemas (7/7) - GML application schemas defining features and feature collections (2/2) - Simple WFS (22/22) - Basic WFS (44/44)

The mapfiles used on the CITE engine are wfs_200_cite.map (Shapefile with OGR connection, require GDAL >= 1.10) and wfs_200_cite_postgis.map.

Note: one of the CITE test consists in sending a REQUEST=GetCapabilities GET request without any SERVICE. As MapServer implements different OGC services in different versions, it is impossible to serve a response that please all specifications together. By default, MapServer sends an HTML error that doesn’t respect WFS 2.0. In order to get CITE compliance, consequently, one needs to define a « wfs_cite_wfs2 » WEB metadata that will return the right exception.

6. Implementation resources

The implementation will be done by Even Rouault with funding from BRGM (Bureau de Recherches Géologiques et Minières).

7. Reference documents

The following documents apply for this development:

8. Voting history

TBD